If cells Values are equal..........then

I have three different cells that i need to compare values between them, and find out if there is a discrepancy in the values

So Column B will have values in B5, B6, B7

i need a formula in B4 that if the values are different then Error

B5 = 100
B6 = 100
B7 = 100

if B6 = 99

then B4 Error, Else OK or any sort of message.

Hi Oceans, If you have solved the problem yourself, please post the solution also. It may help others.